1. Field of the Invention
The present invention relates generally to techniques for assembling systems containing integrated circuit chips or wafers. More specifically, the present invention relates to a method and an apparatus for precisely assembling systems containing semiconductor chips to facilitate proximity communication and power delivery between the semiconductor chips.
2. Related Art
Conductive electrical interconnections and transceivers are generally used to provide reliable communications between integrated circuit (IC) chips in computer systems, due to their packaging and manufacturing advantages. However, decreasing semiconductor line-widths and increasing on-chip clock speeds are putting pressure on the ability of traditional resistive wires to achieve the off-chip bandwidths necessary to fully utilize on-chip computational resources.
A new technique referred to as “proximity communication” overcomes the limitations of conductive connections by using capacitive coupling to provide communications between chips which are oriented face-to-face. This capacitive coupling can provide signal densities two orders of magnitude denser than traditional off-chip communication using wire-bonding or traditional ball-bonding, while the circuits and coupling structures remain fully-compatible with standard CMOS foundries. To communicate off-chip through capacitive coupling, on-chip circuits drive high-impedance, capacitive transmitter pads. Such communication avoids impedance conversion and thereby reduces the power normally dissipated by off-chip driver circuits. Moreover, simple driver circuits and small chip-to-chip distances can significantly reduce the total chip-to-chip communication latency.
While proximity communication provides off-chip signaling bandwidth that scales with chip feature size, it also introduces topological constraints. The active sides of chips typically need to face each other with full or partial overlap, so that corresponding transmitter and receiver pads on opposing chips align both laterally and vertically. Achieving and maintaining chip alignment for proximity communication is challenging, especially when combined with other constraints such as conductive connections for other signals such as power and ground.
Hence, what is needed is a method and an apparatus that facilitates proximity communication and power delivery without the limitations of existing approaches.